Conventionally, there have been known exhaust purification devices in which the NOx catalyst (DCR catalyst) of a selective catalytic reduction type is arranged in the interior of an exhaust pipe, and NOx is reduced to nitrogen and water by use of ammonia as a reducing agent, in order to reduce NOx (nitride oxide) included in exhaust discharged from an internal combustion engine. The urea solution is supplied from a urea solution spray nozzle arranged in the interior of the exhaust pipe into the exhaust, and ammonia is generated from the urea solution by heat of the exhaust, thereby reducing NOx to nitrogen and water.
In the aforementioned exhaust purification device, there is a problem in that the water content of the urea solution remained on the surface of the urea solution spray nozzle evaporates due to the heat of the exhaust, and urea is deposited and grown, which blocks the exhaust pipe. Accordingly, there have been known devices in which a water-repellent coating layer is formed at the tip end of the urea solution spray nozzle, which makes it hard for the urea solution to adhere to the surface of the urea solution spray nozzle. For example, Patent Literature 1 discloses the above-mentioned nozzle.
However, the nozzle disclosed in Patent Literature 1 does not remove the urea solution from the tip end of the nozzle in a positive manner. Accordingly, there is a disadvantage that the urea solution remains on the surface of the nozzle due to a certain direction of the nozzle or a certain shape of the nozzle, and the deposit and growth of the urea cannot be efficiently prevented.